Radial-piston hydraulic motor and method for regulation of a radial-piston hydraulic motor

ABSTRACT

A radial-piston hydraulic motor and method for regulating a radial-piston hydraulic motor including one or more cylinder groups, each cylinder group having piston mechanisms that move radially back and forth. The piston mechanisms include a piston and a press wheel. The volume per revolution of the motor can be changed in one or more stages so that the press wheels of one or more of the piston mechanisms come out of contact with a cam ring. The hydraulic motor also includes a closing valve for closing the flow of working pressure to one or more of the piston mechanisms.

FIELD OF THE INVENTION

The invention concerns a radial-piston hydraulic motor and a method forregulation of a radial-piston hydraulic motor.

BACKGROUND OF THE INVENTION

In the prior art, a number of axial-piston motor constructions areknown, which operate at a high speed of rotation, and with these motors,a high torque is achieved exclusively by connecting the motor with areduction gear at one or several stages. In the present patentapplication, a radial-piston motor construction will be described bywhose means a high torque is achieved at low speeds of rotation. Theconstruction also permits changing of the volume per revolution of themotor in one or several different stages. In this way, an exceptionallywide speed range is obtained by feeding a relatively little volumetricflow through the motor. A motor is provided which has a stepwiseadjustable volume.

OBJECTS AND SUMMARY OF THE INVENTION

According to the invention, the radial hydraulic motor has been formedso that at least one of its piston mechanisms can be switched out ofoperation so as to change the volume per revolution of the motor and,thus, to regulate the speed of rotation and the torque. According to theinvention, the equipment has been formed so that a separate valve,preferably a spindle valve, is used in a stationary stator partconnected with a stationary shaft, which stator part contains the pistonspaces of the piston mechanism. Thus, the valve is fitted in the statorpart between the piston and the distributor valve that revolves as arotor. By means of the valve, the pressurized medium is connected to thepiston and, in a corresponding way, said fluid connection is closed in asituation in which said piston is switched out of operation.

The radial-piston hydraulic motor in accordance with the invention ismainly characterized in that the volume per revolution of the motor canbe changed in one or several stages so that one or several pistonmechanisms can be coupled into the interior of the cylinder group sothat the press wheels of the piston mechanisms come out of contact withthe cam ring, and that there is a closing valve by whose means the flowof the working pressure is connected to the piston mechanism connectedwith the closing valve, or the fluid flow to said mechanism is closed.

The method in accordance with the invention for regulation of aradial-piston hydraulic motor is mainly characterized in that, in themethod, the fluid flow into at least one piston mechanism is closed andopened so that the closing valve is fitted in the cylinder frame of thepiston mechanism, the flow of fluid into the piston mechanism connectedwith the closing valve being closed and opened by controlling theclosing valve.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described with reference to somepreferred embodiments of the invention illustrated in the figures in theaccompanying drawings, the invention being, however, not supposed to beconfined to said embodiments alone.

FIG. 1A is a schematic illustration of the operation of a radial-pistonhydraulic motor.

FIG. 1B is a side view of the equipment shown in FIG. 1A, and, based onthis illustration, the operation of the revolving distributor, i.e. ofthe distributor valve, will be explained in more detail.

FIG. 2 shows the hydraulic diagram of a first preferred embodiment ofthe radial-piston hydraulic motor in accordance with the invention.

FIG. 3 is a sectional view of a hydraulic motor related to theembodiment shown in FIG. 2.

FIGS. 4A, 4B are enlarged views of the closing valve, which is fitted inthe stationary cylinder frame between the piston and the distributorvalve, i.e. distributor, revolving as a rotor. In FIG. 4A the closingvalve is in the position in which the working pressure is passed throughthe closing valve into the piston space of the piston mechanism. FIG. 4Bshows the closing valve in the position in which the control pressurehas been passed to the closing valve and the access of the workingpressure into the piston space has been closed.

FIG. 5 shows the hydraulic motor of FIG. 3 in a stage in which onepiston has been switched out of operation with its press wheel fitted tobe placed out of contact with the cam ring.

FIG. 6 shows the working-pressure ducts placed in the shaft 6 andcommunicating with the exchange valve.

FIG. 7 shows the constructions of the exchange valve and of the relatedpressure relief valve in the shaft 6.

FIG. 8 shows the hydraulic diagram of a second preferred embodiment ofthe invention.

FIG. 9 shows a hydraulic diagram which comprises a flow regulation valveused for regulation of a three-speed motor.

FIG. 10 is a sectional view of the construction of a hydraulic motor inaccordance with the embodiment of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic illustration of the operation of an ordinaryradial-piston hydraulic motor.

The radial-piston hydraulic motor comprises a cylinder group 1 placed ina stationary position. The cylinder group 1 includes a piston mechanism2 that moves radially back and forth. The piston mechanism 2 comprises apiston 2a and a press wheel 2b. Into the piston space 3 of the pistonmechanism 2, hydraulic fluid is passed so that the press wheels 2b ofthe pistons 2a that are in the power stage are pressed with forceagainst the face of the wave-shaped cam ring 4, whereby the ring isbrought into a revolving movement in relation to the cylinder group 1.100a₂ denotes the cylinder frame of the cylinder group 1. A distributorvalve 5 is coupled with the cam ring 4 permanently, which distributorvalve controls the pressurized fluid flow at the correct time into thepiston space 3 of the piston mechanism 2 that is in the power stage. Atthe same time, the distributor valve 5 connects the piston spaces 3 ofthe piston mechanisms 2 that start their return movement to a lowerpressure. The sense of rotation of the motor can be reversed byreversing the direction of the fluid flow through the distributor valve5. The fluid flow is passed to the distributor valve 5 through a set ofducts 7 and 8 placed in the shaft 6, which is non-revolving in relationto the cylinder group 1 in the embodiments illustrated in the figures.Through the duct of higher pressure in the distributor valve 5, theworking pressure is passed, for example, to two pistons that are in thepower stage, while the two pistons that are in a so-called idling stageare then connected to the return flow duct, in which a lower pressure ispresent. In the embodiments shown in the figures, the central shaft 6 isnon-revolving, and the box frame and the related distributor 5, i.e. thedistributor valve, are rotated in relation to said shaft 6. The shaft 6is connected with the non-revolving cylinder frame 100a₂. When a forceacts upon the piston mechanisms and rotates the outside box frame 100a₁,at the same time the distributor, i.e. the distributor valve 5, isrotated and the duct openings present in the distributor aretransferred, in the next stage, from the locations of the pistons in thepower stage to the locations of the pistons in the idling stage, wherebythese pistons enter into the power stage accordingly. Thus, there is arelative movement between the distributor and the cylinder frame, whichis in face contact with said distributor.

FIG. 1B is a side view of the equipment as shown in FIG. 1A. The fluidis passed through annular ducts placed in connection with thedistributor valve 5, i.e. the distributor, into the bore in thedistributor, and through the bores the pressurized medium is passed intoone or several pistons in the power stage so that, when the distributorrevolves, the bores in the distributor that are subjected to fluidpressure meet the bores of the pistons that are in the power stage. Inthe next stage, the pressure spaces are shifted to the following pistonmechanisms, and the pistons in the power stage are now brought intoconnection with the set of return flow ducts. In FIG. 1B, a closingvalve 12 in accordance with the invention is fitted in the cylinderframe 100a₂, by means of which valve 12 the connection of the fluid ofhigher working pressure with the piston space is closed. Thus, saidpiston can be switched off from operation, and thereby the volume perrevolution of the hydraulic motor, i.e. its speed of rotation and itstorque, can be changed.

FIG. 2 shows the hydraulic diagram of a first preferred embodiment ofthe invention. In the embodiment of FIG. 2, there is one cylinder group1 only. In the figure, it is shown that the cylinder group 1 comprisesfour piston mechanisms 2, i.e. the piston mechanisms 2',2",2"' and 2"".Each piston mechanism comprises a piston 2a and a connected press wheel2b, which can be brought into contact with the face of the cam ring 4.In the embodiment shown in FIG. 1, the piston mechanisms 2' and 2" arepiston mechanisms that can be connected out of operation by means of thesolution of equipment in accordance with the invention, whereby thevolume per revolution of the motor can be changed. According to theinvention, this takes place so that, between the piston spaces of thepiston mechanisms 2' and the distributor valve 5, a closing valve 12 isfitted, which can be opened when desired, so that the fluid of highworking pressure enters into the piston space of said piston mechanism,and which valve can be closed in a case in which it is desirable toexclude said piston mechanism from operation, in which case the pistonspace 3 of the piston mechanism is connected to the leakage duct 16. Inthe embodiment of FIG. 2, the closing valves 12a₁,12a₂ and, thus, thepiston mechanisms 2' and 2" are controlled at the same time, and thus,in the embodiment of FIG. 1, there are two modes of operation, i.e. afirst mode, in which all the piston mechanisms 2'. . . 2"" in thecylinder group 1 are in operation, and a second mode, in which just onehalf of the piston mechanisms in the cylinder group 1, i.e. the pistonmechanisms 2"' and 2"" are in operation, whereas the piston mechanisms2',2" have been switched off.

In the following, the various components in the hydraulic diagram ofFIG. 2 and the lines passing to them will be described.

The connections A and B are operation-pressure, i.e. so-calledworking-pressure connections. Through the duct 8, the highest workingpressure is passed to the cylinder group 1, and the return flow at alower pressure passes through the duct 7. When the sense of rotation ofthe motor is reversed, the highest working pressure is passed into theduct 7. The duct 8 comprises the branch points C₁,C₂,C₃, from whichthere are the ducts 8a₁, 8a₂,8a₃ and 8a₄. From the branch point C₁ theduct 8a₁, passes to the exchange valve 9, from the branch point C₂ theline 8a₂ passes to the directional valve 19, and from the branch pointC₃ the branch line 8a₃ passes to the piston mechanism 2"', and from thebranch point C₃ the line 8a₄ passes to the closing valve 12a₁.Similarly, the duct 7 comprises the branch points C_(1a),C_(2a), C_(3a).From the branch point C_(1a) the duct 7a₁, passes to the exchange valve9, from the branch point C_(2a) the branch line 7a₂ passes to thedirectional valve 19, and from the branch point C_(3a) there are thebranch lines 7a₃ and 7a₄, the branch line 7a₃ passing to the closingvalve 12a₂, and the branch line 7a₄ passing to the piston mechanism 2""of the cylinder group 1.

In the solution in accordance with the invention, the closing valves12a₁ and 12a₂ are so-called spindle valves, whose function is to passthe working pressure from one end of the spindle valve through thespindle valve to the piston mechanism connected with the spindle valveof the cylinder group 1 when the spindle is in one of its end positionsand when the control pressure does not act upon the annular space 13 inthe spindle valve. If the control pressure has access into the space 13at the other end of the spindle valve, by means of the control pressurepassed into said space the spindle 12b can be shifted into the otherextreme position, in which case the connection from the pressure line 8to said piston mechanism of the cylinder group 1 is closed, and thepiston and the piston space 3 of the piston mechanism concerned arebrought, through the annular space 15 in the spindle 12b, intoconnection with the leakage line 16a₁ of the motor and further with theleakage line 16a₃. A similar operation takes place in respect of theclosing valve 12a₂.

In the embodiment of FIG. 2, there are two closing valves, i.e. 12a₁ and12a₂.

The operation of the directional valve 19 is as follows. Depending onthe line, i.e. the line 7a₂ or the line 8a₂, into which the higherpressure enters, the spindle of the valve 19 is displaced so that theconnection from the pressure line 7a₂ /8a₂ to the line F₁ and to thepressure relief valve 20 is opened, i.e that the lower-pressure line ofthe working pressure lines 7 or 8 is connected to the line f₁ andthrough the pressure relief valve 20 to the box space 17.

From the exchange valve 9, the line f₂ passes to the speed-change valve10, so that, when the control pressure is passed into the line 11, thespindle of the valve 10 is shifted so that the line f₂ is brought intoconnection with the line f₃, which further communicates with the closingvalves 12a₁,12a₂ through the branch lines f₄ and f₅ so as to controlsaid closing valves and thereby to transfer the control pressure intoconnection with the spindles 12b of said closing valves, so that theclosing valves 12a₁,12a₂ close the pressure lines 8 passing to thepistons connected with said closing valves. From the closing valves12a₁,12a₂, the lines 16a₁, 16a₂ pass to the leakage line 16a₃.Similarly, when no pressure is passed into the control line 11, the linef₂ is closed, and the line f₃ communicates with the leakage line 16a₄through the valve 10. In such a case, the leakage lines 16a₁,16a₂ and16a₃ still communicate with the box space 17 of the hydraulic motorthrough the check valve 21.

The coupling 50 is brought into the open position and, thus, the brakingoperation is switched off when the control pressure is passed into theline f₆ and a piston or equivalent, for example lamellae 52, aredisplaced so that they are brought out of contact with the backingpiece. Then, the locking between the rotatable box 100a₁ and the shaft 6is opened. The spring force of the spring 51 keeps the coupling engaged.When no control pressure is passed into the line f₆, the coupling 50 isalways in the closed position by the effect of the spring force of thespring 51.

In FIG. 2, the contours of the motor have been drawn with broken lines,and the connections passing to/from the motor have been indicated withthe letters A,B,Y,C, and D. The connection D serves for operation of thecoupling, the connection C is the connection to the box space 17, theconnection Y is the input connection for the control pressure of thespeed-change valve, and the connections A and B are connections for theoperating pressure, i.e. so-called working pressure connections.

Operation of a two-speed motor

According to the invention, the volume per revolution of theradial-piston motor can be reduced by closing the feed of the fluid flowinto the piston space 3 of one or several piston mechanisms 2. Thistakes place so that the higher working pressure of the motor is passedthrough the exchange valve 9 to the speed-change valve 10. Thespeed-change valve 10 is switched by connecting the control pressure tothe control line 11 of the speed-change valve 10. The speed-change valve10 connects the higher working pressure of the motor to a particularannular space 13 also in the closing valve 12. Then, the closing valve12 closes the feed of the fluid flow from the working-pressure duct 8 tothe piston space 3 of the piston mechanism 2. If desired, it can beensured that the closing valve 12 remains closed by using a larger areaat the side of the spring housing 13 in the closing valve as comparedwith the opposite end of the closing valve 12. By using a particulardistributor duct, which is denoted with the general reference numeral14, between the speed-change valve 10 and the closing valves 12, it ispossible to close the feed to one or several piston mechanisms 2 at thesame time. The duct 14 comprises duct portions f₃,f₄ and f₅, as isindicated in FIG. 2. Said closing valve 12 is shaped so that, at thesame time as it closes the supply of the fluid flow into the pistonspace 3 of the piston mechanism 2, it connects said piston space 3 witha pressure-free space 15. This pressure-free space 15 is an annularduct, which again communicates with the leakage line 16 of the motor. Insuch a case, when revolving in relation to the stationary cylinder group1, the wave-shaped form of the cam ring 4 presses the entire pistonmechanism 2, by the intermediate of the press wheel 2b of the piston 2a,into the interior of the cylinder group 1. Then, the press wheel 2b ofthe piston mechanism 2 loses its contact with the face of the cam ring4.

The holding of the piston mechanism 2 in the interior of the cylindergroup 1 can be ensured by forming a difference in pressure between thepiston space 3 of the piston mechanism 2 and the box space 17 of themotor. This is produced by throttling the leakage fluid flowing out ofthe box space 17 of the motor by means of a springloaded check valve 18.

According to the invention, the shifting of the piston mechanism 2 intothe cylinder group 1 can be intensified by means of a separate set ofvalves 19,20. The set of valves 19,20 includes a directional valve 19,which operates by means of a difference in pressure so that, of the twoworking-pressure ducts 7 and 8 of the motor, it connects the duct withthe lower pressure into connection with the pressure relief valve 20,through which pressure relief valve 20 the desired fluid flow isdischarged into the box space 17 of the motor and fills the shortagethat tends to be formed in the box space 17 of the motor as thewave-shaped cam ring 4 presses one or several piston mechanisms 2, bythe intermediate of the press wheel 2b, into the cylinder group 1. Thisset of valves 19,20 contributes to permitting a change in the volume perrevolution also at high speeds of rotation of the motor, because thepiston mechanism 2 is transferred more quickly into the cylinder group 1and the press wheel 2b of the piston 2a does not tend to be struckagainst the face of the wave-shaped cam ring 4.

According to the invention, the shifting of the piston mechanism 2 intothe cylinder group 1 can also be made quicker by means of a check valve21. The check valve 21 is placed so that it short-circuits the pistonspaces 3 of the piston mechanism 2 through the system of ducts 15,16with the box space 17 of the motor. When the wave-shaped cam ring 4presses one or several piston mechanisms 2, by the intermediate of thepress wheel 2b, into the cylinder group 1, a vacuum tends to be formedin the interior of the box space 17 of the motor, which vacuum is,however, equalized with the aid of said check valve 21. In other words,the fluid flow that is discharged out of the piston space 3 of thepiston mechanism 2 is passed through the system of ducts 15,16, in thefree flow direction of the check valve 21, into the box space 17 of themotor. After the piston mechanisms 2 moved fully into the cylinder group1 and the press wheels 2b of the pistons 2a were separated from the camring 4, the check valve 21 is closed as the leakage fluid dischargedinto the box space 17 of the motor or the fluid flow that had been fedinto the box space 17 earlier by means of said set of valves 19,20 formsa pressure in the box space 17 of the motor when the flow is throttledby the spring-loaded check valve 18 mentioned above.

When the control line 11 of the speed-change valve 10 is connected witha pressure-free space outside the motor, the spring 22 presses thespeed-change valve 10 back into its original position. Then, thespeed-change valve 10 connects the spring housings 13 of the closingvalves 12 through the distributor duct 14 to the pressure-free space 15.When no control pressure is passed to the closing valve 12, the pressureof the working pressure shifts the spindle 12b of the closing valve 12into a position in which the connection from the working-pressure duct 8through the closing valve 12 into the piston space 3 of the pistonmechanism is opened, and the cylinder concerned is brought into contactwith the cam ring 4. In its connection, the spindle 12b of the closingvalve 12 includes a spring, which presses the spindle 12b of the closingvalve 12 into a position that closes the duct 8 when no pressure hasbeen passed into the duct 8. In such a case, the fluid in the pistonspace 3 communicates with the leakage duct 16 through the space 15 ofthe valve 12. When pressure is passed to the closing valve 12, theclosing valve 12 closes the connection of the piston space 3 with thepressure-free space 15 and, at the same time, opens the duct from thedistributor valve 5 to the piston space 3. The fluid flow presses thepress wheel 2b of the piston mechanism 2 into contact with the cam ring4 and produces a higher torque of the motor when the press wheel ispressed against the wave-shaped face of the cam ring 4. Then, the motorhas its maximal volume per revolution.

FIG. 3 is a sectional view of the construction of the motor shown inFIG. 2. The sectional view shows the piston mechanisms 2' and 2"'. Therevolving box frame 100a₁ of the device comprises a cam ring 4 and adistributor valve 5 that revolves along with the box 100a₁. Thedistributor valve 5, i.e. the distributor, comprises bores m₁,m₂ . . . ,which communicate both with the working-pressure line 8 and with thereturn line 7. When the box 100a₁ revolves, the distributor valve 5,i.e. the distributor, which revolves along with the box, communicatesthrough pressure lines with the ducts n₁,n₂ . . . placed in the cylinderframe 100a₂, which is the stator in the stationary shaft 6. The cylinderframe 100a₂ comprises piston bores 3 for the piston of each pistonmechanism. Further, for example, exactly the piston mechanism 2'includes a closing valve 12a₁ placed in the cylinder frame 100a₂. Thespeed-change valve 10 is fitted in the stationary shaft 6, and the duct11 is passed as parallel to the shaft 6 to the speed-change valve 10.

When the piston mechanism 2' is closed out of operation, the controlpressure is passed along the line 11 in the shaft 6 to the speed-changevalve 10, to the end of its spindle 10a, and the spindle is controlledagainst the spring force of the spring 22 into a position in which theworking pressure is controlled from the line f₂ through the valve 10 tothe line f₃ and from it into the annular space 14 and further into thespring housing 13 in the closing valve 12a₁. Then, the spindle 12b ofthe closing valve 12a₁ is shifted by the effect of the pressure into aposition (to the left in the figure) in which the connection from thepressure line 8 through the distributor valve 5 to the cylinder frame100a₂ and, thus, to the piston 2' is closed.

In the embodiment of FIG. 3, the cam ring 4 is connected with therotatable box frame 100a₁, with which the distributor 5, i.e. thedistributor valve, is also connected. The shaft 6 is in a stationaryposition, and so is the cylinder frame 100a₂, which is connected withthe shaft by means of a grooved joint. The box frame 100a₁ is rotated inrelation to the shaft 6 on support of bearings G₁,G₂.

FIG. 4A shows the area of the piston mechanism 2' from FIG. 3 on anenlarged scale. The press wheel 2b of the piston mechanism is in contactwith the cam ring 4. Then, the control pressure is passed to the closingvalve 12, whereby the closing valve 12 admits the working pressure intothe piston space 3.

FIG. 4B shows the area of the piston mechanism 2' from FIG. 5 on anenlarged scale. The press wheel 2b of the piston mechanism is placedapart from the cam ring 4.

The closing valve 12 in the closed position, and no control pressurearrives in the closing valve.

FIG. 5 shows the closing valve 12a₁ in the closed position, in whichposition the piston mechanism 2' has been pressed into the cylinderframe 100a₂, into the piston space 3 in the cylinder frame, and in whichposition the press wheel of the mechanism is placed apart from the camring 4.

FIG. 6 shows the working-pressure ducts 8 and 7, which communicate withthe exchange valve 9.

FIG. 7 shows the location of the valves 19 and 20 in the stationaryshaft 6. It is shown in the figure that the duct 8 is the duct at ahigher pressure, and the pressure in the duct 8 is passed through thebores 8a₂ ',8a₂ " passing from said pressurized duct into the end 19c ofthe bore 19b of the spindle 19a of the valve 19. Similarly, from thereturn duct 7, the fluid of lower pressure is passed through the ducts7a₂ ',7a₂ " to the valve 19. As is shown in the figure, since thepressure present in the space 19c is higher than the pressure in thespace 19d, the spindle 19a has been shifted into the position shown inthe figure, and from the duct 7 of lower pressure the fluid is passedthrough the valve 19 to the pressure relief valve 20 and further intothe box space 17. The spring forces of the valve 20 and of the spring20a₁ are adjustable. By means of the valve 20, the flow into the space17 is controlled.

FIG. 8 shows a second embodiment of the invention, which is related to athree-speed motor. The hydraulic diagram of a three-speed motor isshown. As is shown in the hydraulic diagram in FIG. 8, the solution ofequipment comprises two cylinder groups: the cylinder groups 1 and 24.Each cylinder group comprises piston mechanisms; the cylinder group 1comprises the piston mechanisms 2',2",2"' and 2"", and the cylindergroup 24 comprises the piston mechanisms 23',23",23"', 23"". Thehydraulic diagram of FIG. 8 is in the other respects similar to thehydraulic diagram of FIG. 2, except that, in this solution, two cylindergroups are used, in whose cylinder groups the press wheels 2b,23b of thepiston mechanisms are in contact with the cam ring 4. In the solution, athree-position speed-change valve 10 is used. The speed-change valve 10comprises a control-pressure line 11 connected to the end of itsspindle, into which pressure line two control pressures of differentpressure levels can be passed. If no control pressure is passed, thespeed-change valve 10 is in a position in which the spindles 12b of theclosing valves 12a₁ . . . 12a₆ related to the piston mechanisms are in aposition in which the pressurized fluid flow from the working-pressureduct has access into the piston spaces in the piston mechanismsconnected with said closing valves. If a first pressure, which is lowerthan a second pressure, is passed into the control line 11, the spindle10a of the speed-change valve 10 is shifted into a position in which apart of the closing valves, i.e. the closing valves 12a₃ . . . 12a₆ areswitched on, i.e. to close the access of the working pressure into thepiston mechanisms. When the higher pressure is passed into thespeed-change valve 10 along the control-pressure line 11, the spindle10b of the speed-change valve 10 is shifted into a position in which thecontrol pressure is controlled to all of the closing valves 12a₁ . . .12a₆ of the cylinder groups 1,24. When no control pressure isintroduced, the spindle of the speed-change valve 10 is shifted backinto its original position, and all the piston mechanisms are inoperation.

The hydraulic diagram shown in FIG. 8 is to a great extent similar tothe hydraulic diagram of the embodiment described above. In thehydraulic diagram of FIG. 8, the high-pressure working pressure ispassed along the duct 8, and the return line 7 has a lower workingpressure. If it is desirable to reverse the sense of rotation of themotor, the working pressures passed into the connections A and B areinterchanged.

The line 8 comprises the branch points C₁,C₂,C₃, from which there arethe branch duct 8a₁ to the valve 9, the branch duct 8a₂ to the valve 19,and the branch ducts 8a₃ and 8a₄ from the branch point C₃. The branchduct 8a₄ passes to the directional valve 12a₁, and the branch duct 8a₃is branched from the branch point C₃ ' to the piston mechanism 2"' ofthe cylinder group 1 and to the closing valve 12a₆. Similarly, thereturn line 7 comprises the branch points C_(1a),C_(2a),C_(3a),C'_(3a).From the branch points C_(1a),C_(2a), C_(3a), there are the duct 7a₁ tothe valve 9, the duct 7a₂ to the valve 19, and the duct 7a₃ to theclosing valve 12a₂, and from the branch point C_(3a), there is a furtherline 7a₄ to the branch point C'_(3a), from which there are the lines 7a₄' and 7a₄ ". The line 7a₄ ' passes to the mechanism 2"" of the cylindergroup 1, and from the branch point C_(3a) ', moreover, the duct 7a₄ "passes to the closing valve 12a₅.

From the valve 9, a pressure duct f₂ passes to the speed-change valve10, and from the speed-change valve 10 there are outlets f₇ and f₈ forcontrolling the closing valves 12a₁ . . . 12a₆.

As is shown in FIG. 8, the duct 14 passes to the closing valves12a₁,12a₂. The duct 14 comprises duct portions f₇,f₇ ',f₇ ".

Similarly, from the valve 10, there is a control duct 27 to the closingvalve 12a₃, 12a₄,12a₅ and 12a₆ of each piston mechanism. The duct 27comprises the duct portions f₈,f₈ ',f₈ ", f₉,f₁₀,f₁₁,f₁₂. For the sakeof clarity of illustration, the leakage ducts passing from the closingvalves 12a₁ . . . 12a₆ are denoted with the general reference numeral16.

Operation of a three-speed motor in more detail

It is characteristic of the radial-piston hydraulic motor equipment inaccordance with the invention shown in FIG. 8 that one or severalclosing valves 12 mentioned above can be placed in the cylinder groups1,24 depending on the number of piston mechanisms 2,23 that are supposedto be coupled in the cylinder group 1,24. If there are several cylindergroups 1,24 in the motor, several different volumes per revolution canbe obtained by coupling the piston mechanisms 2,23 inside the cylindergroup in several different stages. In the construction shown, there aretwo cylinder groups 1,24 placed side by side, each of which contains apiston mechanism 2,23 of its own. The press rolls 2b,23b of the pistonsin the cylinder groups 1,24 may roll along the face of a common cam ring4, or there may be a cam ring 4 of its own for each cylinder group. Thedepth of the wave in the cam rings 4 may also differ from one another.

Also, the diameters of the pistons 2a,23a may be different in thecylinder groups 1,24. By means of combinations of these alternatives,several different combinations of volume per revolution are obtainedadvantageously.

The construction shown includes a valve system 10', in which threedifferent volumes per revolution can be obtained by means of the samecontrol-pressure connection 11. This has been accomplished by using athree-position speed-change valve 10. In the first position of thespeed-change valve 10, when no control pressure is passed into itscontrol-pressure line 11, the motor is connected to full volume perrevolution. In such a case, the piston mechanisms 2,23 of both of thecylinder groups 1,24 are, by the intermediate of the press wheels2b,23b, in contact with the cam ring 4 and produce a full torque whilesubjected to the working pressure. Then, the annular spaces in theclosing valves 12 in both cylinder groups 1,24, i.e. the spring housings13,26, communicate through the system of ducts 14,27 with thespeed-change valve 10 and through said valve further with thepressure-free spaces 15,28 of the closing valves, and from said spacesthey communicate with the leakage line 16 of the motor and therebypermit flow of the fluid through the distributor valve 5 into the pistonspaces 3,29 of all piston mechanisms 2,23 in both cylinder groups 1,24.

In the second position of the speed-change valve 10, which is producedby feeding a first pressure level into the control-pressure line 11,this pressure level produces a movement of the speed-change valve 10against a first pre-tensioned spring 22. The speed-change valve 10 movesuntil it collides against a stop 30, against which a second spring 31 ispre-tensioned. This spring 31 has been tensioned at a higher, secondpressure level; thus, this first pressure level with which thespeed-change valve 10 is displaced cannot compress it, but the movementof the speed-change valve 10 stops against this stop 30. In thisposition, the speed-change valve 10 closes the connection of the springhousings 26 of the closing valves 25 of the cylinder group 24 with thepressure-free space 28 and passes the higher pressure of theworking-pressure duct 7 and 8 through the exchange-check valve 9 intothe spring housings 26 of the closing valves 12 of the first cylindergroup 24, whereby the spring housings 26 are closed and connect thepiston spaces 29 of the piston mechanisms 23 to the pressure-free space28. Then, the piston mechanisms 23 of said first cylinder group 24 moveinto the interior of the cylinder group 24 while the wave-shaped camring 4 presses them by means of the press wheels 23b. This movement canbe made quicker by means of the system of valves 18,19,20,21 describedabove. In this way, the second range of volume per revolution of themotor has been reached.

The third position of the speed-change valve 10 is produced by, to thecontrol line 11 of the speed-change valve 10, connecting a secondpressure level, which is higher than the first pressure level. Thissecond pressure level acts upon the speed-change valve 10 with a forcehigher than the force to which the second spring 31 that limits thespindle has been pre-tensioned. In this way the speed-change valve 10 isshifted further to the third position against the mechanical limiter 32.

In this third position, the speed-change valve 10 closes the connectionof the spring housings 13 of the closing valves 12 in the secondcylinder group 1 with the pressure-free space 15 and connects the higherworking pressure through the system of ducts 14 to the spring housing(s)13 of one or several closing valve(s) 12 in the second cylinder group 1,thereby closing the closing valves 12 and connecting the piston spaces 3of the piston mechanisms 2 to the pressure-free space 15. In this way,one or several of the piston mechanisms 2 in this second cylinder group1 also move(s) into the cylinder group 1, and the contact of the presswheels 2b of the pistons 2a of the piston mechanisms 2 with the cam ring4 ends. The shifting of the piston mechanisms 2 into the cylinder group1 can be made quicker by means of the system of valves 18,19,20,21described above. In this third position of the speedchange valve 10, thehigher one of the working pressures of the motor still communicates withthe spring housings 26 of the closing valves 12a₃ . . . 12a₆ of thefirst cylinder group 24, and thus, the piston mechanisms 23 of the firstcylinder group 24 remain coupled inside the cylinder group 24. In thisway, the third range of volume per revolution of the motor has beenreached.

Switching of the motor back to full volume per revolution takes placeeither stepwise by controlling the first pressure level to the controlline 11 of the speed-change valve 10, in which case the speed-changevalve 10 is shifted to its second position by the effect of the secondpre-tensioned spring 31. Then the speed-change valve 10 connects thespring housings 13 of one or several closing valves 12 of the secondcylinder group 1 to the pressure-free space 15.

Then the closing valves 12 in the cylinder group 1 close the connectionof the piston spaces 3 of the piston mechanisms 2 with the pressure-freespace 15 and, at the same time, open the flow duct for the feed comingfrom the distributor valve 5 into the piston spaces 3 of the pistonmechanisms 2. Then the piston mechanisms 2 are shifted, by theintermediate of the press rolls 2b, into contact with the wave-likeshape of the cam ring 4 and produce a higher torque of the motor. Inthis way, the second range of volume per revolution of the motor hasbeen reached.

If the control-pressure line 11 of the speed-change valve 10 is furtherconnected to the pressure-free space outside the motor, the speed-changevalve 10 moves into its first position by the effect of the forceproduced by the first pre-tensioned spring 22. Then, through the systemof ducts 27, the speed-change valve 10 connects the spring housings 26of the closing valves 12a₃ . . . 12a₆ in the first cylinder group 24 tothe pressure free space 28, and in this way the piston mechanisms 23 ofthis cylinder group 24 are also shifted, by the intermediate of thepress wheels 23b, into contact with the cam ring 4 in the way describedabove, again producing a higher torque of the motor. In this way, themotor has again been connected to its full volume per revolution.

The speed-change valve 10 can also be lowered directly from the thirdposition to its first position by connecting the control-pressure line11 directly at once to the pressure-free space outside the motor. Then,the motor is connected directly, in the way described above, to the fullvolume per revolution.

Flow regulation valve

In the hydraulic diagram in FIG. 9, a flow regulation valve 33 is shown.According to the invention, in connection with the exchange-check valve9 and the speed-change valve 10 mentioned above, while making use ofsaid valves, a flow regulation valve 33 can be connected, through whichthe desired fluid flow can be tapped under control from theworking-pressure duct 7 or 8 of higher pressure of the motor whileby-passing the distributor valve .5 and the piston mechanisms 2,23 ofthe motor. Said fluid flow is discharged through the box space 17 of themotor into the leakage line 16 of the motor and through it into the tankof the system.

In the solution that is shown, the speed-change valve 10 has been formedso that this by-pass flow takes place exclusively when the motor is inthe range of full volume per revolution. The higher working pressurecoming from the exchange-check valve 9 is connected through the groovein the speed-change valve 10 to the system of ducts 34, which passes tothe flow regulation valve 33. When the flow passes through the smallhole 35 in the flow regulation valve 33, a difference in pressurearises, and the lower pressure level thus produced is transferred intothe spring housing in the flow regulation valve 33 and has the effectthat the flow regulation valve 33 moves forwards so that the edge in theflow regulation valve 33 starts throttling the fluid that flows out fromthe flow regulation valve 33. In this way, a state of equilibriumarises, and the flow regulation valve 33 attempts to maintain aninvariable fluid flow through the flow regulation valve 33 irrespectiveof the level of working pressure. The force applied to the flowregulation valve 33 by the loss of pressure arising in the small hole 35in the flow regulation valve 33 is equal to the force of the spring thatloads the flow regulation valve 33. Such a controlled by-pass flow isnecessary when it is desirable to rotate the motor particularly slowly.This comes from the fact that the output regulation means of thehydraulic pump which feeds pressurized fluid to the radial-pistonhydraulic motor do not necessarily operate evenly with very smallvolumetric flows.

At the stages two and three of the speed-change valve 10, the valvecloses the flow to the flow regulation valve 33, and no by-pass flowtakes place.

FIG. 10 is a sectional view of a radial-piston hydraulic motor inaccordance with the embodiment as shown in FIG. 8. As is shown in FIG.10, the speed-change valve 10 is placed in the non-revolving centralshaft 6, and from the speed-change valve 10, ducts pass to the cylinderframe 100a₂, which is likewise placed in a stationary, non-revolvingposition. In the solution, the box frame 100a₁ and the connected camring 4 as well as the distributor valve 5 connected with the box frame100a₁ revolve by means of the pistons of the piston mechanisms in thestationary cylinder groups. The embodiment shown in FIG. 10 is to agreat extent similar to the embodiment shown in FIG. 2. The shaft 6 isstationary and non-revolving, and the cylinder group 100a₂ is connectedwith the shaft 6, preferably by means of a groove joint non-revolvingly.In relation to the shaft 6 and to the cylinder group 100a₂, the boxframe 100a₁, and the connected cam ring 4 and also the distributor 5connected with said construction are rotated by means of the workperformed by the pistons. Between the shaft 6 and the box frame 100a₁,there are bearings G₁,G₂.

The invention is not supposed to be confined exclusively to anembodiment in which the central shaft is non-revolving and the cylindergroup and the cylinder frame are non-revolving, but the solution ofequipment is also applicable to a case in which the central shaft 6 isrotated and, correspondingly, the cylinder frame revolves, in which casethe stator part and its distributor valve 5 are in a stationary,non-revolving position.

I claim:
 1. A radial-piston hydraulic motor, comprisinga central shaft;at least one cylinder group, each of said at least one cylinder groupcomprisinga cylinder frame including a plurality of radially orientedrecesses and arranged in a stationary position in connection with saidshaft; a box frame rotatably mounted to said cylinder frame, a cam ringhaving an inner, wave-shaped face arranged in connection with said boxframe, piston mechanisms having a piston and a press wheel and arrangedin said recesses in said cylinder frame such that a piston space isdefined between said cylinder frame and each of said pistons, andconduit means for passing hydraulic fluid into said piston spaces suchthat said pistons are pressable against said wave-shaped face of saidcam ring to cause said cam ring to revolve in relation to said at leastone cylinder group; a distributor valve connected to said box frame forcontrolling flow of the hydraulic fluid to and from said piston spacesvia said conduit means in order to selectively displace at least some ofsaid pistons in a power stage outward against said cam ring causing saidcam ring to rotate while enabling other of said pistons in a returnstage to be displaced inward, a set of ducts arranged in said cylinderframe for passing the hydraulic fluid to said distributor valve, aclosing valve arranged in said cylinder frame and interposed betweensaid distributor valve and at least one of said piston spaces, saidclosing valve including a movable spindle structured and arranged tocontrol the flow of hydraulic fluid to said at least one piston spaceindependent of the flow of hydraulic fluid to other of said pistonspaces, and connecting means for fluidly connecting said distributorvalve to said closing valve such the hydraulic fluid flows from saiddistributor valve through said closing valve to said at least one pistonspace.
 2. The motor of claim 1, wherein said distributor valve ispermanently attached to said cam ring such that said distributor valverotates about said shaft.
 3. The motor of claim 1, further comprisingbearing means for rotatably mounting said box frame to said cylinderframe.
 4. The motor of claim 1, wherein said distributor valve includesa plurality of bores communicating with each of said ducts in said setof ducts and arranged such that at any given time, a portion of saidbores communicate with respective ones of said conduit means leading tosaid pistons in the power stage and another portion of said borescommunicate with respective ones of said conduit means leading to saidpistons in the return stage.
 5. The motor of claim 1, furthercomprisinga speed-change valve arranged in said shaft for controllingmovement of said spindle in said closing valve and thus the flow ofhydraulic fluid to said at least one piston space, and a duct arrangedin said shaft substantially parallel to the orientation of saidspeed-change valve in said shaft and in fluid communication with saidspeed-change valve such that a control fluid is passed through said ductto said speed-change valve.
 6. The motor of claim 5, wherein saidspeed-change valve includes a spindle and a spring for biasing saidspindle against the pressure exerted by the control fluid.
 7. The motorof claim 1, wherein said closing valve comprises a spring housing inwhich said spindle is situated and which defines a pressure-freespace,further comprising a leakage line arranged in said shaft andcommunicating with said pressure-free space, said spindle having a firstposition in which the hydraulic fluid flows from said distributor valveto said at least one of said piston spaces and a second position inwhich the hydraulic fluid flows from said at least one of said pistonsthrough said press-free space in said spindle to said leakage line. 8.The motor of claim 7, further comprisingan exchange-check valve, and atleast one speed-change valve fluidly coupled to said exchange-checkvalve, said exchange-check valve being structured and arranged such thatthe hydraulic fluid in the set of ducts having a higher pressure ispassed through said exchange-check valve to said at least onespeed-change valve, said at least one speed-check valve passing thehydraulic fluid into said spring housing of said closing valve to movesaid spindle.
 9. The motor of claim 7, wherein a box space of the motoris defined between said cylinder frame and said box frame, furthercomprisinga directional valve, a pressure-relief valve in fluidcommunication with said directional valve and said box space, aspring-loaded check valve in fluid communication with said box space andsaid leakage line, whereby when the hydraulic fluid passes through saiddirectional valve to said pressure-relief valve and into said box spaceand from said box space through said spring-loaded check valve into saidleakage line, the inward movement of said pistons in the return stageinto said recesses is made quicker, and a difference in pressure isformed between said piston spaces and said box space such that thepressure in said box space is higher than the pressure in said pistonspaces to ensured that said pistons remain in said recesses.
 10. Themotor of claim 9, further comprisinga check valve structured andarranged to ensure that a vacuum is not formed in said box space whensaid pistons are moved into said recesses.
 11. The motor of claim 9,further comprising a flow regulation valve structured and arranged toenable fluid flow therethrough into said box space such that the fluidflow by-passes said distributor valve and said piston spaces when themotor is at a maximum volume per revolution.
 12. A method for regulatinga radial-piston hydraulic motor including a central shaft and at leastone cylinder group, each of said at least one cylinder group comprisinga cylinder frame including a plurality of radially oriented recesses andarranged in a stationary position in connection with said shaft, a boxframe rotatably mounted to said cylinder frame, a cam ring having aninner, wave-shaped face arranged in connection with said box frame,piston mechanisms having a piston and a press wheel and arranged in saidrecesses in said cylinder frame such that a piston space is definedbetween said cylinder frame and each of said pistons, and conduit meansfor passing hydraulic fluid into said piston spaces such that saidpistons are pressable against said wave-shaped face of said cam ring tocause said cam ring to revolve in relation to said at least one cylindergroup, the improvement comprising the steps of:connecting a distributorvalve to said box frame for controlling flow of the hydraulic fluid toand from said piston spaces via said conduit means in order toselectively displace at least some of said pistons in a power stageoutward against said cam ring causing said cam ring to rotate whileenabling other of said pistons in a return stage to be displaced inward,arranging a set of ducts in said cylinder frame for passing thehydraulic fluid to said distributor valve, arranging a closing valve insaid cylinder frame between said distributor valve and at least one ofsaid piston spaces, said closing valve including a movable spindlestructured and arranged to control the flow of hydraulic fluid to saidat least one piston space independent of the flow of hydraulic fluid toother of said piston spaces, and fluidly connecting said distributorvalve to said closing valve such the hydraulic fluid flows from saiddistributor valve through said closing valve to said at least one pistonspace.